Researchers at San Diego State University and the University of Arizona swabbed chairs, phones, computer mice, computer keyboards and desktops at 90 randomly chosen offices in New York, San Francisco and Tucson, Ariz. They found more than 500 types of bacteria populating the offices — with more in men’s workspaces than in women’s.

“Humans are spending an increasing amount of time indoors, yet we know little about the diversity of bacteria and viruses where we live, work and play,” said lead author Dr. Scott Kelley of San Diego State University, in a statement. “This study provides detailed baseline information about the rich bacterial communities in typical office settings and insight into the sources of these organisms.”

Most of the bacteria originated from the office workers themselves, spread by coughing, sneezing and shedding of skin, for example. The researchers also found a surprising number of bugs associated with the human digestive tract and several that are commonly found in feces.

As gross as that sounds, Kelley says it isn’t really cause for concern. “[Bacteria] are with you all the time and don’t make you sick,” says Kelley. “Most are either harmless or helpful to us. We tend to focus on the few that make us ill, but we encounter thousands of different types every day in our environment.”

The germiest spots in your office, in case you’re wondering: your chair and your phone. Further, Kelley found, the surfaces in offices inhabited by men tended to have 10% to 20% more living bacteria than those used by women. Kelley speculates that’s because men are larger than women and simply have more skin surface area for bacteria to breed on. “Men are also somewhat less hygienic than women so that could factor in as well,” says Kelley.

Interestingly, previous research has found the opposite, with women’s offices having more germs than men’s, possibly due in part to the fact that women use cosmetics and are more likely to store food in their desks, ABC News reported. The discrepancy between the studies could be attributable to the different methods used to detect bacteria, Philip Tierno, a clinical professor microbiology and pathology at NYU Langone Medical Center, who was not affiliated with the current study, told ABC News: to pick up germs, Kelley’s study used molecular methods, which are more sensitive than identification methods used in some previous studies.

Just last week, a separate study by researchers at Kimberly-Clark Professional also used a molecular detection method to gauge the germ count in typical office spaces. For that study, researchers swabbed areas all over the office, not just in people’s personal workspaces. They found that the dirtiest spots, with the highest levels of an organic molecule signaling bacterial contamination were as follows:

75% of break room sink faucet handles

48% of microwave door handles

27% of keyboards

26% of refrigerator door handles

23% of water fountain buttons

21% of vending machine buttons

The current study, which was partly funded by Clorox, was published in the journal PLoS ONE.